What is Psoriasis

Psoriasis is a common, chronic (persists for a long period of time) skin condition. People who suffer from psoriasis develop red, scaly patches that can also be itchy. White or silvery scales can also form over these patches, which is quite characteristic of psoriasis.

Psoriasis is a complex disease and much remains to be understood on how it develops. It is known that patches of psoriasis contain many abnormally activated immune cells within them. The most effective treatments for psoriasis are known to suppress immune cell activity. Research has established that certain inheritable genes predispose people to develop psoriasis.

For more information about the subtypes of psoriasis and how they can be diagnosed, see Psoriasis Subtypes.

Statistics on Psoriasis

The incidence of psoriasis peaks at ages 16 to 22 and 57 to 60. There are similar rates in men and women; however, rates vary greatly between different races and populations. The rate also varies by latitude, which is thought to be due to different levels of sunlight exposure. One study found that 2% of the population in the United States has some form of psoriasis. Another study found that having a family history of psoriasis greatly increases the lifetime risk of developing psoriasis.

Risk Factors for Psoriasis

Psoriasis probably occurs due to a combination of genetic and environmental factors. This includes stress, some types of infections and certain drugs (such as lithium and beta-blockers). Psoriasis is more common at higher than lower latitudes and is more common in Caucasians than other races.

Approximately 30% of people with psoriasis have an immediate family member who is also affected. Psoriasis vulgaris is more common in the immediate and extended family of individuals with the disease than in the general population. Children who have both parents and a sibling with psoriasis have an 83% chance of developing the disease.

Progression of Psoriasis

Relatively little is known regarding the progression of psoriasis, or factors that predict the severity of disease. As most cases of psoriasis commence during teenage years and early adulthood, the majority of individuals are affected for most of their lives. Psoriasis is called ‘early onset’ if it occurs before the age of 40.

It is thought that psoriasis will self-resolves in around a third of people. However, the disease can last for long periods, even up to 50 years. Of people with psoriasis vulgaris, 80% will have mild to moderate disease, while 20% have moderate to severe psoriasis (affecting more than 5% of the body surface area or affecting hands, feet, face, or genitals). If severe psoriasis is untreated, it tends to fluctuate in severity. Comparatively, mild to moderate psoriasis tends to wax and wane over time.

Psoriasis may take one of several forms and each has characteristic symptoms and potential severity. The types of psoriasis include psoriasis vulgaris, flexural/inverse psoriasis, guttate psoriasis, erythrodermic psoriasis, generalised pustular psoriasis, palmoplantar psoriasis, scalp psoriasis and nail psoriasis.

Psoriasis vulgaris (plaque psoriasis)

Psoriasis vulgaris (also known as chronic plaque psoriasis) is characterised by raised, rough plaques with surrounding normal skin. It is the most common form of psoriasis, affecting 80–90% of individuals. The plaques can be salmon-pink or red and are generally distributed symmetrically on the body. They are covered with white or silvery scales.

Flexural psoriasis (inverse psoriasis)

Flexural (inverse) psoriasis is a rare form of psoriasis that occurs in areas where two layers of skin come together, such as the groin, armpits, buttocks and below the breast. Flexural psoriasis appears as shiny red plaques that are not covered with scales, this is due to the moist areas in which they occur.

Guttate psoriasis

Guttate psoriasis generally affects children and young adults. Sufferers develop small salmon-pink, teardrop-shaped bumps (less than 1 cm in diameter) and are usually covered with a fine scale. This generally occurs on the trunk and upper arms and legs. It occurs approximately 2 to 3 weeks following a viral or bacterial upper airway infection, such as tonsillitis.

Erythrodermic psoriasis

Erythroderma is a rare, potentially life-threatening form of psoriasis. The skin becomes bright red and inflamed, with variable degrees of scale. Over 75% of the body surface is affected which can lead to fever, chills, fatigue, hypothermia, heart failure and infection.

Generalised pustular psoriasis

Generalised pustular psoriasis is another rare, serious form of psoriasis. Sufferers develop fevers and chills and pustules form all over the body. Small pustules can form in acutely painful, inflamed skin all over the body. It is caused by infections, medications (such as corticosteroids) or pregnancy.

Palmoplantar psoriasis

In palmoplantar pustulosis, painful, itchy yellow-brown pustules form on the palms of the hands and soles of the feet. These pustules are typically 2–5 mm in diameter, yellow and evolve into a dusky-red, crusted, bumpy rash.

Scalp psoriasis

Scalp psoriasis is common in people with chronic plaque psoriasis, usually within the hairline but the entire scalp can be affected. Plaques are typically covered with thick white or silvery scales, however it does not cause hair loss.

Nail psoriasis

Around half of all people with psoriasis have fingernail changes associated with the disease, while 35% have toenail changes. The most common nail change is the formation of small pits within the nail. Other changes can include separation of the nail plate, dots of yellow-orange discolorations within the nail or breakdown of the entire nail.

For more information about the subtypes of psoriasis and how their macroscopic features, see Psoriasis Subtypes.

Symptoms of Psoriasis

People with psoriasis may find they are less productive, have altered moods (depression or anxiety) and experience difficulties with social interaction. It is important to tell your doctor about the severity of these symptoms, as this will help determine the intensity of treatment and allow for provision of adequate support.

People have different responses to treatments, so the effectiveness and side effects of previous treatments plays an important role in guiding current and future treatment options.

Clinical Examination of Psoriasis

The diagnosis of psoriasis is based on the appearance of the psoriasis-affected skin. Characteristic nail changes and classical distribution of plaques are also strongly suggestive of psoriasis. A doctor’s examination of a person with psoriasis aims to determine the severity of disease:

Mild psoriasis is defined as affecting less than 10% of the body’s surface area;

Moderate psoriasis affects more than 10%, or less than 10% in difficult areas; and

Severe disease affects more than 20%.

Clinicians use a specific method to assess severity of psoriasis, called the Psoriasis Area and Severity Index (PASI). Moderate to severe disease is defined as a PASI score greater than 10. The PASI is also used to determine if individuals are responding to treatment over time.

The effect of psoriasis on a person’s quality of life needs to be considered when assessing the severity of disease. For example, mild psoriasis on the palms and soles may have a significant impact on day-to-day life and may require different medications. Doctors also examine psoriasis sufferers for evidence of an infection, which can cause other problems for people with psoriasis.

Some other conditions that can have a similar appearance to psoriasis are:

How is Psoriasis Diagnosed?

Special tests for psoriasis are generally not required. Diagnosing psoriasis and determining the severity of disease is based almost entirely on clinical examination. Occasionally, biopsies can be taken from a psoriasis plaque to confirm the diagnosis.

Prognosis of Psoriasis

Psoriasis is known to have a significant impact on quality of life that may result in profound affects on mental health and reduced participation in employment. There is an increased overall risk of death in individuals with severe psoriasis.

Psoriasis is associated with several diseases, including:

Cardiovascular disease: There is an increased risk of cardiovascular disease in individuals with moderate or severe psoriasis. This is thought to be due to increased immune system activation due to psoriasis. Individuals with psoriasis are also frequently overweight and have higher rates of diabetes and high blood pressure. There does not appear to be an increased risk of cardiovascular disease in individuals who have only mild psoriasis;

Metabolic syndrome:Metabolic syndrome is more common in individuals admitted to hospital with psoriasis than in hospitalised people who do not have psoriasis;

Cancer:Skin cancer is more common in people with psoriasis. It is unclear whether the link between psoriasis and cancer is due to the treatment of psoriasis or the condition itself. There is a controversial link between lymphoma and psoriasis;

Depression: Up to 60% of individuals with psoriasis may have depression and 5% reported active suicidal ideation; and

How is Psoriasis Treated?

Treatment considerations

Severe psoriasis has many affects on the lives of people who suffer from the disease. This can make it difficult to comply with treatment for psoriasis. Individuals may find cognitive behavioural therapy beneficial, as it has been shown to improve compliance with medication and control of symptoms.

The management of psoriasis is tailored to suit each individual. The extent and location of the psoriasis, as well as other illnesses, quality of life, triggering factors and ability to use different treatments can affect the selection of medications.

As a chronic condition that can affect your quality of life, your doctor will provide you with education on aspects of the illness, such as:

A long-term approach to treatment, including likely prognosis, cost/benefit of treatments, future life events (e.g. pregnancy) and the possible effect of psoriasis on quality-of-life.

Topical therapy

Topical therapies (treatments applied to the surface of the area they are intended to treat) can be applied directly to psoriasis as creams or ointments and are generally safe. They are the best approach in treating psoriasis over smaller areas and they can also reduce the need for, or dose of, other medications.

Topical corticosteroids

Topical corticosteroids suppress immune system activity. They are the first choice for plaque, scalp or intertriginous psoriasis and are available in varying strengths. Lower strength steroids are reserved for the face, thin-skinned areas and on children. They are often used in combination with other topical therapies, phototherapy or oral medications.

Topical corticosteroids do have some side effects, such as acne, skin infections or dermatitis. They can also exacerbate other underlying skin conditions if used for long periods of time. More serious side effects are very rare. If individuals are using strong doses, very frequent application and/or over a large surface area, side effects are more likely.

Vitamin D analogues

The vitamin D analogues (substances that are similar in structure to vitamin D) include calcipotriene, calcipotriol (e.g. Daivonex, Daivobet) and calcitriol. They slow down the overgrowth of skin tissue characteristic of psoriasis. These drugs take longer to work than topical corticosteroids but tend to be effective for longer periods. The use of corticosteroids with vitamin D analogue therapy is more effective than using either treatment alone. Skin irritation is the most common side effect, affecting up to 35% of people.

Tazarotene

Tazarotene (e.g. Zorac) is a topical retinoid that decreases skin overgrowth and inflammation. Tazarotene is often used in combination with topical corticosteroids. Skin irritation and heightened sensitivity to sunlight are possible side effects.

Dithranol

Dithranol (also known as anthralin) was a common treatment for psoriasis, but it is used less commonly as it can stain skin and clothing. Dithranol is an effective treatment that can be used in combination with phototherapy, topical corticosteroids or calcipotriol.

Calcineurin inhibitors

Calcineurin inhibitors such as tacrolimus (e.g. Prograf, Tacrolimus Sandoz) and pimecrolimus (e.g. Elidel) stop the production of inflammatory chemicals that cause psoriasis to evolve. They are generally only used for facial or intertriginous psoriasis. They can, however, cause burning and itching, but this generally reduces with ongoing use.

Salicylic acid

Salicylic acid causes softening and lifting of psoriasis scales. The combination of topical salicylic acid with a topical corticosteroid is more effective than using just topical corticosteroids. It can cause skin irritation.

Emollients

Emollients increase skin hydration and are used in combination with other psoriasis treatments. They can reduce the mount of scale and decrease itchiness of psoriasis and they have minimal side effects.

Coal tar

Coal tar has been used as a treatment for psoriasis for many decades. It is available as solutions, shampoos and ointments. It can also be used as combination with phototherapy. However, individuals using coal tar often complain of skin irritation, skin infections, staining of clothing and an unpleasant smell.

Phototherapy

Phototherapy is a commonly used treatment for psoriasis, where the skin is exposed to ultraviolet (UV) light to inhibit skin overgrowth. Phototherapy is effective in younger people with thin psoriasis and in individuals who say sunlight improves their symptoms. Phototherapy uses narrow band UV-B light as it is more effective than other types. Moderate psoriasis is generally cleared after 6 weeks of phototherapy three times a week. This can give 3 to 6 months of symptom relief.

Phototherapy can have side effects. This includes skin redness, itchiness, burning and stinging of the skin. The skin can also age prematurely. However, there is no evidence of increased risk of skin cancer. Using new lasers, phototherapy can now be targeted specifically on psoriasis-affected areas, while leaving unaffected skin untreated.

PUVA photochemotherapy

PUVA is the combination of the medication psoralen and UVA phototherapy. This is used in individuals with a long history of psoriasis that doesn’t respond to UVB phototherapy, people with thick scales or if the hands, soles or nails are involved. UVA has similar effects to UVB, but can penetrate deeper into the psoriasis plaques.

Common side effects of PUVA treatment include skin redness, itchiness, pigmentation of the skin and nausea and vomiting. With long-term PUVA therapy, most individuals will have skin aging and there is an increased risk of cataracts.

Systemic therapy

Systemic therapies are medications that are taken orally and circulate around the entire body. These drugs are used in individuals with psoriasis that is not controlled by topical agents or phototherapy, but they carry a higher risk of side effects.

Cyclosporin

Cyclosporin inhibits the activity of immune cells. It is used in palmoplantar pustulosis, erythrodermic and nail psoriasis. It is a safe treatment to use in women who are trying to fall pregnant. Cyclosporin works quickly and can stop the symptoms of psoriasis for long periods. The major side effects are high blood pressure and kidney toxicity. Cyclosporin can only be used for 1 to 2 years. Cyclosporin may also be a good treatment option for people with hepatitis C infection.

Methotrexate

Methotrexate is the most used treatment for moderate to severe psoriasis. Methotrexate is generally well tolerated and can be used long-term. However, it is not safe to be used during pregnancy or for women who are trying to fall pregnant. Men taking methotrexate should avoid conceiving while taking the drug. Men should also take folic acid supplements while on methotrexate. Because methotrexate is associated with liver disease, extra consideration should be given to cases where alcohol use disorder is present.

Acitretin

Acitretin (e.g. Neotigason, Acitretin Actavis) is a medication that inhibits immune dysfunction causing psoriasis. It takes 3 to 6 months to reach maximum effect. It can be combined with other topical treatments (corticosteroids or vitamin D analogues). Individuals may experience side effects such as conjunctivitis, hair loss, skin dryness, nail fragility, high cholesterol and osteoporosis.

Biologic agents

New biological therapies can specifically target the chemicals and enzymes responsible for the development of psoriasis. These medications are a major advance in treating moderate to severe psoriasis. They are more effective and less toxic than other systemic therapies. However, they are very expensive and they are only used in specific individuals who have moderate to severe disease or are unresponsive to other treatments.

T cell modulators – alefacept and efalizumab (neither is currently available in Australia);

IL-12/IL-23 inhibitors – ustekinumab (e.g. Stelara).

TNF alpha antagonists

These drugs bind and inactivate the inflammatory chemicals that cause psoriasis to progress. They are given intravenously; however, 24% of people experience a reaction at the injection site. Over 20% of individuals experience side effects during the injection, such as chills, headache, flushing and dyspnoea.

T cell modulators

Alefacept and efalizumab target immune cells critical to the development of psoriasis. However, neither is available in Australia. These drugs are generally less effective than other biological agents and require careful monitoring of white cell counts. The main side effects are fatigue and joint pain, which occurs in approximately 20% of people treated with alefacept.

IL-12/IL-23 inhibitors

Ustekinumab is a drug that binds and inactivates two chemicals (IL-12 and IL-23) that stimulate the development of moderate to severe psoriasis. Ustekinumab has very few side effects and injection site reactions are uncommon. It is currently available in Australia.